1. Field of Invention
This invention relates to automobile trailers, specifically to an improved mechanism to lower the frame of the trailer to ground level.
2. Discussion of Prior Art
The traditional towed trailer has a rigid axle on which the wheels are rotatably supported. The axle is disposed beneath the load floor of the trailer. The body of the trailer is supported above the axle by leaf springs. Two or more shock absorbers are employed between the axle and the trailer floor to dampen the road vibrations. Depending on the load to be transported on the trailer, the wheel will have a rolling radius between twelve and twenty-two inches. This will position the trailer floor approximately eighteen to thrity inches above the ground.
The trailers generally do not have a tiltable or drop down body portion which requires the use of ramps to assist in loading the components onto the trailer. The ramps must be stored on the trailer during towing so that they will be available for unloading the components. Alternatively, the trailer can be detached from the towing vehicle and tilted at the rear axle to facilitate loading. However, the angle at which the trailer must be titlted is quite large which makes the loading or heavy items very difficult and hazardous.
Several prior trailer designs for lowering to ground level from a raised travel position have been developed over the years and are known in the art. The prior art trailer has a bed which is lowered to the ground using a winch operation such that the bed does not tilt when being raised or lowered. When using the prior art trailer, a piece of equipment is positioned or moved onto the lowered bed. The bed is then raised by a winch into an elevated position so that the bed can clear the ground. Operation of this prior art trailer included the raising or lowering by using a hand or automatic winch and cable which pulled the bed into a raised position. The prior art trailer required a great amount of power to raise the bed and the equipment thereon to the raised position. In addition, the failure of a rope, pulley or winch on the prior art trailer would result in damage to the trailer, the objects placed upon the trailer and possible injury to individuals.
The prior art trailer also was held in position by a standard type of toggle retaining latch to secure the bed to the frame once the bed was in the raised travel position. It is extremely important that the bed be properly secured in the raised position such that the objects being hauled are not damaged and that no injury occurs to individuals.
Similarly, U.S. Pat. No. 4,490,089 to Welker describes a motorcycle trailer having two principal assemblies connected together in a hinged arrangement at the rear ends thereof. One of the assemblies may be lowered to rest flat almost on the ground by a cooperative levering action with the other assembly, and by reversing such action the load-bearing assembly can be raised to a level position above ground. The single axle connecting the wheels does not obstruct the lowering of the load-bearing assembly because the axle has an offset movable configuration whereby a center portion thereof can be made to lie on the ground. The load-bearing platform can be lowered as far as such center portion, but can only be as wide as the center portion, which limits the load to a single motorcycle.
U.S. Pat. No. 4,685,855 to Celli is for another two-part system employing a tilting assembly hingedly connected at its rear end to a load platform. This design forces the load-carrying bed to move forward and backward as well as up and down, requiring the entire framework not including the tongue to be longer than the load platform, with wasted space forward of the platform and a portion of the platform overhanging its rear support. Additionally the wheels are mounted on stub axles attached to the main supporting framework, but no particular attachment means is described. Thus, the potential for torsion of the stub axles relative to the frame is not addressed.
U.S. Pat. No. 5,308,213 to Gilbertson is for another ground level loading trailer employing a lever member hingedly connected at its rear end to the load platform. In order for the load-bearing platform to be lowered to ground level, the trailer tongue must tilt upward to the rear, pivoting at the point of attachment to the towing vehicle. The patent discloses a conventional ball hitch mechanism. The angle of tilt of the tongue can be no greater than the angle at which the forward lip of the means for engaging the ball is stopped by the surface on which the ball is mounted. Again, there is no common axle, and there is no provision for limiting torsion action of the stub axles with respect to the frame.
U.S. Pat. No. 4,930,799 to Pihlstrom et al. describes another dual element trailer wherein the load is placed on a pallet lying flat on the ground behind the main trailer frame. The main frame is tiltable and supported by wheels mounted on a conventional common axle. When the frame is in its tilted position, it becomes a ramp onto which the pallet is drawn by means of a hand-operated winch. When the pallet is aligned properly on top of the frame, the frame is pivoted to a horizontal travel position. This design does not present a torsion problem due to the common axle. However, there are some drawbacks to this invention: the fact that more room is required to accommodate the pallet when it is on the ground behind the main frame, and the lack of levering action at the rear end of the load platform to improve mechanical advantage. The heaviest loads probably could not be pulled up the ramp with a hand-operated winch.
Other prior trailer designs included those which involve pushing or driving the load onto a ramp or tilting platform in order to reach the travel position above ground level, because the supporting wheels are connected by a conventional common axle which obstructs lowering of a load platform to a position flat on the ground. With this type of trailer, pushing a heavy ATV up a ramp typically requires two or more people. There is a danger of serious injury to those trying to load heavy wheeled vehicles on such a trailer. In addition, the entire trailer body is not able to be lowered to ground level, thereby precluding its use as an ice fishing house.